desktop screen problem

I did that multiple times but it still shows those line (you can see the link to the picture above) my monitor shows this lines when it's black or when I'm doing other things.(i took the picture of my monitor when it's black, so the lines would be easier to see)
 
Better replace the monitor as it might be an issue with the screen itself or u might want to reset the settings of ur monitor using the settings on the monitor buttons.Hope this helps:)